Polymer composite material having oriented electrically and thermally conductive pathways

ABSTRACT

A method of forming a polyolefin-perovskite nanomaterial composite which contains oriented electrically and thermally conductive pathways. The method involves milling a polyolefin with particles of a perovskite nanomaterial, molding to forma composite plate, and subjecting the composite plate to an AC voltage. The AC voltage forms oriented electrically and thermally conductive pathways by partial dielectric breakdown of the composite. The presence of the oriented electrically and thermally conductive pathways gives the polyolefin-perovskite nanomaterial electrical and thermal conductivity and dielectric permittivity higher than the polyolefin alone.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. application Ser. No.16/828,443, now allowed, having a filing date of Mar. 24, 2020. Thepresent application is related to U.S. application Ser. No. 16/989,367,having a filing date of Aug. 10, 2020, now U.S. Pat. No. 10,899,092which is a Continuation of U.S. application Ser. No. 16/828,443.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a method of preparing apolyolefin-perovskite nanomaterial composite utilizing application of anAC voltage, and a polyolefin-perovskite nanomaterial composite made bythe method, optionally having oriented electrically and thermallyconductive pathways.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Polyolefins have a number of properties that are advantageous forapplications in a wide variety of products and industries such asconsumer goods, packaging, medical products, and safety equipment.Specifically, the low electrical and thermal conductivity of polyolefinshelp to prevent the risk of electrical shock or thermal burns. The samelow electrical and thermal conductivity, however, is disadvantageous foruse in certain electronics applications where higher values of theseproperties are desirable.

A common strategy for changing the physical properties of polymers is tocreate polymer composites by blending other materials with the polymer.Such composites may have altered characteristics such as dielectricpermittivity, electrical conductivity, Young's modulus, flexibility,toughness, degradation resistance, and others. The inclusion ofnanomaterials into polyolefins is often done to enhance theelectrically-insulating nature of the polyolefin. The incorporation ofsome types of nanomaterials causes an increase in the dielectricbreakdown strength and a decrease in the dielectric permittivity of thecomposite compared to the polyolefin alone [Ma, et. al., Nanotechnology,2005, 16, 6, 724—incorporated herein by reference in its entirety]. Thisdecrease in dielectric permittivity and increased dielectric breakdownstrength is attributed to the ability of the nanomaterial to change thespatial charge distribution in the polyolefin matrix and to reduce theinternal electric field produced in the composite upon voltageapplication [Easaee, et. al., Journal of Nanomaterials, 2018, Article ID7921725—incorporated herein by reference in its entirety]. Further, thedielectric breakdown strength of polyolefins is increased due to theability of the nanomaterial to suppress “electrical treeing”, thedendritic growth of electrically conductive pathways in the polyolefinmatrix caused by partial dielectric breakdown [Tanaka, 2016, In: PolymerNanocomposites, Huang X., Zhi C. (eds), Springer, Cham—incorporatedherein by reference in its entirety]. The particles of the nanomaterialact as termination points for the electrically conductive pathways,suppressing the continued growth and branching. While the decrease inthe dielectric permittivity may be advantageous for creating a highlyinsulating polyolefin material for insulating applications, this lowerdielectric permittivity may be disadvantageous for other applications.

A polyolefin-based composite with higher electrical and thermalconductivity and higher dielectric permittivity compared to thepolyolefin alone, however, would be advantageous for use in electronicsapplications. Such a composite could take advantage of the properties ofthe polyolefin such as flexibility, toughness, and degradationresistance and have the required electrical and thermal conductivitiesfor applications such as batteries, solar cells, electrodes, orelectronics packaging. Such a material would rely on careful choice ofthe appropriate nanomaterial and processing or preparation methods toachieve increased, as opposed to decreased, dielectric permittivity.

In view of the foregoing, one objective of the present invention is toprovide a method for preparing a polyolefin-nanomaterial composite withhigher electrical and thermal conductivity and higher dielectricpermittivity compared to the parent polyolefin by the incorporation of aperovskite nanomaterial. It is a further objective of the presentinvention is to provide a nanocomposite material having increaseddielectric permittivity and electrically and thermally conductivepathways, e.g., formed from application of AC voltage.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to a methodof making a polyolefin-perovskite nanomaterial composite comprisingmixing a perovskite nanomaterial with a polyolefin powder to form amixture, ball milling the mixture in a high-energy shaker to form acomposite powder, molding the composite powder to form a compositeplate, and subjecting the composite plate to an AC voltage of 1 to 50kV/mm to form the polyolefin-perovskite nanomaterial composite.

In some embodiments, the AC voltage has a frequency of 50 to 70 Hz.

In some embodiments, the polyolefin-perovskite nanomaterial compositecomprises a polyolefin matrix, particles of a perovskite nanomaterialuniformly distributed in the polyolefin matrix, and orientedelectrically and thermally conductive pathways.

In some embodiments, the polyolefin matrix is present in thepolyolefin-perovskite nanomaterial composite in an amount of 90 to 99 wt%, and the perovskite nanomaterial is present in thepolyolefin-perovskite nanomaterial composite in an amount of 1 to 10 wt%, each based on a total weight of the polyolefin-perovskitenanomaterial composite.

In some embodiments, the AC voltage is applied by placing the compositeplate on a supporting ground electrode and placing a needle electrodeinto the composite plate such that the needle electrode does not contactthe supporting ground electrode and the supporting ground electrode andneedle electrode are separated by a distance of at least 30% of athickness of the composite plate.

In some embodiments, the supporting ground electrode, the compositeplate, and the needle electrode are immersed in a non-conductive liquidmedium during the subjecting.

In some embodiments, the oriented electrically and thermally conductivepathways comprise dendritic conductive channels in the polyolefin matrixwhich originate and terminate at at least one selected from the groupconsisting of an exterior surface of the composite, a channel created bythe needle electrode, and a particle of the perovskite nanomaterial.

In some embodiments, an oriented electrically and thermally conductivepathway, optionally together with one or more additional pathways and/orone or more particles of perovskite nanomaterial, comprises a path alongwhich electricity may flow that spans a thickness of thepolyolefin-perovskite nanomaterial composite.

In some embodiments, the polyolefin is polyethylene.

In some embodiments, the polyethylene is low density polyethylene.

In some embodiments, the low density polyethylene has a density of 0.88to 0.96 g/cm³ and a melt flow index of 0.2 to 2.5 g/10 minutes.

In some embodiments, the perovskite nanomaterial is barium titanatenanoparticles.

In some embodiments, the composite plate has a real dielectricpermittivity of 2.0 to 3.0 at 1 kHz.

In some embodiments, the polyolefin-perovskite nanomaterial compositehas a thermal conductivity of 0.1 Wm⁻¹K⁻¹ to 500 Wm⁻¹K⁻¹, an electricalconductivity of 10⁻¹² S/m to 10² S/m, and a dielectric permittivity of3.1 to 50 at 1 kHz.

The current disclosure also relates to a polyolefin-perovskitenanomaterial composite, comprising a polyolefin matrix in an amount of90 to 99 wt %, based on a total weight of the polyolefin-perovskitenanomaterial composite, perovskite nanomaterial present in an amount of1 to 10 wt %, based on a total weight of the polyolefin-perovskitenanomaterial composite, and oriented electrically and thermallyconductive pathways comprising either hollow channels in the polyolefinmatrix or material formed from electrical damage of the polyolefinmatrix that has a distinct chemical composition from the polyolefinmatrix.

In some embodiments, the polyolefin matrix comprises polyethylene.

In some embodiments, the polyethylene is low density polyethylene.

In some embodiments, the low density polyethylene has a density of 0.88to 0.96 g/cm³ and a melt flow index of 0.2 to 2.5 g/10 minutes.

In some embodiments, the perovskite nanomaterial is barium titanatenanoparticles.

In some embodiments, the oriented electrically and thermally conductivepathways comprise dendritic conductive channels in the polyolefin matrixwhich originate and terminate at least one selected from the groupconsisting of an exterior surface of the composite, a channel created bythe needle electrode, and a particle of the perovskite nanomaterial.

In some embodiments, the polyolefin-perovskite nanomaterial compositehas a thermal conductivity of 0.1 Wm⁻¹K⁻¹ to 500 Wm⁻¹K⁻¹, an electricalconductivity of 10⁻¹² S/m to 10² S/m, and a dielectric permittivity of3.1 to 50 at 1 kHz.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic representation of the application of the ACvoltage showing the needle electrode (101), composite plate (102),non-conductive liquid medium (103), and supporting ground electrode(104);

FIG. 2A is a schematic representation of the application of the ACvoltage showing the needle electrode, polymer matrix, BaTiO₃nanoparticles, supporting ground electrode, and the initiation of anoriented electrically and thermally conductive pathway at the site ofthe needle electrode under application high AC voltage;

FIG. 2B shows propagation and branching of an oriented electrically andthermally conductive pathway and the beginning formation of thedendritic structure of the oriented electrically and thermallyconductive pathways;

FIG. 2C shows complete formation of dendritic structure of the orientedelectrically and thermally conductive pathways with complete paths alongwhich electricity may flow.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present disclosure will now be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments of the disclosure are shown.

The present disclosure will be better understood with reference to thefollowing definitions. As used herein, the words “a” and “an” and thelike carry the meaning of “one or more.” Within the description of thisdisclosure, where a numerical limit or range is stated, the endpointsare included unless stated otherwise. It will be further understood thatthe terms “comprises” and/or “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

As used herein, the words “about,” “approximately,” or “substantiallysimilar” may be used when describing magnitude and/or position toindicate that the value and/or position described is within a reasonableexpected range of values and/or positions. For example, a numeric valuemay have a value that is +/−0.1% of the stated value (or range ofvalues), +/−1% of the stated value (or range of values), +/−2% of thestated value (or range of values), +/−5% of the stated value (or rangeof values), +/−10% of the stated value (or range of values), +/−15% ofthe stated value (or range of values), or +/−20% of the stated value (orrange of values). Within the description of this disclosure, where anumerical limit or range is stated, the endpoints are included unlessstated otherwise. Also, all values and subranges within a numericallimit or range are specifically included as if explicitly written out.

As used herein, “composite” refers to a combination of two or moredistinct constituent materials into one continuous or discontinuousmass. The individual components, on an atomic level, remain separate anddistinct within the finished structure. The materials may have differentphysical or chemical properties, that when combined, produce a materialwith characteristics different from the original components. In someembodiments, a composite may have at least two constituent materialsthat comprise the same empirical formula but are distinguished bydifferent densities, crystal phases, or a lack of a crystal phase (i.e.an amorphous phase).

According to a first aspect, the present disclosure relates to a methodof making a polyolefin-perovskite nanomaterial composite. The methodinvolves first mixing a perovskite nanomaterial with a polyolefin powderto form a mixture. In some embodiments, the polyolefin powder is presentin an amount of 90 to 99 wt %, preferably 95 to 98 wt %, preferably 96to 97.75 wt %, preferably 96.5 to 97.5 wt %, preferably 97 wt % based ona total weight of the mixture. In some embodiments, the perovskitenanomaterial is present in an amount of 1 to 10 wt %, preferably 2 to 5wt %, preferably 2.25 to 4 wt %, preferably 2.5 to 3.5 wt %, preferably3 wt % based on a total weight of the mixture.

Examples of polyolefins include polyethylene, polypropylene,polymethylpentene, polybutene-1, polyisobutylene, polystyrene, polyvinylchloride, polybutadiene, and the like. In some embodiments, thepolyolefin is polyethylene. In some embodiments, the polyethylene islow-density polyethylene (LDPE). In preferred embodiments, thepolyolefin is LDPE having a density of 0.88 to 0.96 g/cm³, preferably0.89 to 0.95 g/cm³, preferably 0.90 to 0.94 g/cm³, preferably 0.91 to0.93 g/cm³. In preferred embodiments, the polyolefin is LDPE having amelt flow index of 0.2 to 2.5 g/10 minutes, preferably 0.25 to 1 g/10minutes, preferably 0.3 to 0.5 g/10 minutes, preferably 0.35 to 0.45g/10 minutes, preferably 0.40 g/10 minutes. In some embodiments, theLPDE is in the form of particles having a particle size distributionwherein greater than 90% of particles, preferably greater than 91% ofparticles, preferably greater than 92% of particles, preferably greaterthan 93% of particles, preferably greater than 94% of particles,preferably greater than 95% of particles have a particle size less than600 μm, preferably less than 575 μm, preferably less than 550 μm,preferably less than 525 μm, preferably less than 500 μm.

As used herein “perovskite” refers to a material which has theperovskite structure type. The perovskite structure type is a structureadopted by materials which have the general formula ABX₃, where A and Bare cations which have a ratio of charge on cation A to charge on cationB of 1:2 and X is an anion. Typical ion charge combinations are A⁺B²⁺X⁻₃ and A²⁺+B⁴⁺X²⁻ ₃. The perovskite structure type is characterized bythe presence of an octahedral coordination of the B cation by X anions.These octahedra are arranged in a cubic lattice and are vertex-sharing.The A cations occupy pockets with cubic symmetry defined by 8 of theoctahedra. Typically, the arrangement of the octahedra and A cationsforms a material with cubic symmetry, however slight distortions maylower the symmetry of the material, for example to tetragonal ororthorhombic. Examples of such distortions include shifts of the Bcations such that they are not in the center of the octahedra(off-centering) and tilting of the octahedra such that the center of theoctahedra remain in a cubic arrangement, but the orientation of theoctahedra results in a non-cubic symmetry. The perovskite structure typeis named after a mineral called perovskite, composed of calcium titanate(CaTiO₃), which crystallizes in the cubic perovskite structure type. Theaforementioned mineral is a member of the class of materials known as“perovskites”. Examples of other perovskites include simple perovskites,complex perovskites, layered perovskites, and hybrid perovskites.

Simple perovskites are perovskites which have chemical formulas whichconform to the chemical formula explained above. Simple perovskites haveonly one type of atom occupying the B cation sites in the perovskitestructure or fulfill the B cation position in the aforementionedchemical formula. Simple perovksites may have one or more type of atomoccupying the A cation sites in the perovskite structure or fulfill theA cation position in the aforementioned chemical formula. Simpleperovksites may have one or more type of atom occupying the X anionsites in the perovskite structure of fulfill the X anion position in theaforementioned chemical formula. This description also covers dopedperovskites that are doped in both the A and X sites in the structure ofA and X positions in the chemical formula. Examples of simpleperovskites include calcium titanate (CaTiO₃, perovskite), bridgmanite((Mg,Fe)SiO₃), bismuth niobate (BiNbO₃), barium titanate (BaTiO₃),strontium titanate (SrTiO₃), strontium zirconate (SrZrO₃), lead titanate(PbTiO₃), bismuth ferrite (BiFeO₃), lanthanum ytterbium oxide (LaYbO₃),lanthanum strontium manganite ((La,Sr)MnO₃), yttrium aluminum perovskite(YAlO₃, YAP), lutetium aluminum perovskite (LuAlO₃, LuAP), CsPbI₃,CsGeBr₃, RbPbI₃, CsSnBr₃, and RbSbI₃.

Complex perovskites are perovskites that have more than one type of atomoccupying the B cation sites in the perovskite structure of fulfill theB cation position in the aforementioned chemical formula. Complexperovskites may be disordered complex perovskites or ordered complexperovskites. Disordered complex perovskites are complex perovskiteswhere the B cation sites in the perovskite structure are filled with arandom distribution of cations able to occupy said sites based on thechemical composition of the material. No long range ordering of the Bcations exists. Examples of disordered complex perovskites include leadzirconate titanate (Pb(Zr,Ti)O₃, PZT), lead ferrite tantalate(Pb(Fe,Ta)O₃), lead scandium tantalate (Pb(ScTa)O₃, PST) bariummanganite titanate (Ba(Mn,Ti)O₃, BMT), and barium manganite niobate(Ba(Mn,Nb)O₃, BMN). Ordered complex perovskites are complex perovskiteswhich have long range order and symmetry to the cations occupying the Bcations sites in the perovskite structure. An example of ordered complexperovskites are double perovskites, which have a 1:1 mixture of twodifferent B cations, labeled B and B′. Double perovskites are denotedwith the formula AB_(0.5)B′_(0.5)X₃ or A₂BB′X₆. Double perovskites havea similar crystalline unit cell as perovskites, but with dimensions thatare twice as large as the parent, simple perovskites. Other examples ofordered complex perovskites have B:B′ cation ratios of 1:2(AB_(0.33)B′_(0.67)X₃) or 1:3 (AB₀₂₅B′_(0.75)X₃). Examples of orderedcomplex perovskites include Sr₂FeMoO₆, Sr₂NiIrO₆, andBaZn_(0.33)Ta_(0.67)O₃.

Layered perovksites are materials in which sheets of the ABX3 structureare separated by sheets of a different material. Layered perovskites maybe classified based on the chemical formula of the different materialinto Aurivillius phase, Dion-Jacobson phase, and Ruddlesden-Popper phaselayered perovskites. Aurivillius phase layered perovskites are materialsin which the different material comprises [Bi₂O₂]²⁺ ions occurring everyn layers (where n is an integer from 1 to 5) to give a material with theoverall formula Bi₂A_((n−1))B_(n)O_((3n+)) or [Bi₂O₂]-A_((n−1))B_(n)O_((3n+1)). Examples of Aurivillius phase layered perovskitesinclude [Bi₂O₂] BiTi₂O₇, Bi₂MoO₆, and SrBi₂Nb₂O₉. Dion-Jacobson phaselayered perovskites are materials in which the different material iscomposed of an alkali metal layer ever n layers (where n is an integerfrom 1 to 5) to give a material with the overall formulaMA_((n−1))B_(n)O_((3n+1)) where M is an alkali metal. Examples ofDion-Jacobson phase layered perovskites include KLaNb₂O₇, CsLaNb₂O₇,CsBa₂Ta₃O₁₀, and KSr₂Nb₃O₁₀. Ruddlesden-Popper phase layered perovskitesare materials in which the different material is a layer of cations A′,which may be any cations that would occupy an A cation site in aperovskite material, occurring every n layers, where n=1 or 2, givingthe material the overall formula A′_(n)A_((n−1))B_(n)O_((3n+1)).Examples of Ruddlesden-Popper layered perovskites include Sr₂RuO₄,Sr₃Ru₂O₇, Sr₂TiO₄, Ca₂MnO₄, and SrLaAlO₄.

Hybrid perovskites are perovskite materials in which one or more of thecations is an organic cation such as ammonium, organoammonium,formamidinium. Examples of hybrid perovskites include methylammoniumlead iodide (CH₃NH₃PbI₃), methylammonium tin bromine (CH₃NH₃SnBr₃), andformamidinium lead iodide (NH₂CHNH₂PbI₃).

In some embodiments, the perovskite nanomaterial is a simple perovskitematerial. In alternative embodiments, the perovskite material is acomplex perovskite, a layered perovskite, or a hybrid perovskite. Inpreferred embodiments, the perovskite nanomaterial is barium titanate.

In some embodiments, the perovskite nanomaterial is in the form ofnanoparticles. In some embodiments, the nanoparticles have a mean sizeof 100 to 500 nm, preferably 125 to 475 nm, preferably 150 to 450 nm,preferably 175 to 425 nm, preferably 200 to 300 nm. In some embodiments,the nanoparticles may have a spherical shape, or may be shaped likecylinders, boxes, blocks, spikes, flakes, plates, ellipsoids, toroids,stars, ribbons, discs, rods, granules, prisms, cones, platelets, sheets,angular chunks, terraced cubes, terraced rectangular prisms, or someother shape. In some embodiments, the nanoparticles may be substantiallyspherical, meaning that the distance from the nanoparticle centroid(center of mass) to anywhere on the nanoparticle outer surface varies byless than 30%, preferably by less than 20%, more preferably by less than10% of the average distance. In some embodiments, the nanoparticles arein the form of blocks, granules, terraced rectangular prisms, or angularchunks, having a mean size in a range as previously described and havinga largest dimension that is 50 to 500%, preferably 75 to 400, preferably100 to 350%, preferably 150 to 250% of the range previously describedand a smallest dimension that is 5 to 150, preferably 10 to 125,preferably 15 to 100, preferably 25 to 75% of the range previouslydescribed. In some embodiments, the nanoparticles may be in the form ofagglomerates. As used herein, the term “agglomerates” refers to aclustered particulate composition comprising primary particles, theprimary particles being aggregated together in such a way so as to formclusters thereof, at least 50 volume percent of the clusters having amean size that is at least 2 times the mean size of the primaryparticles, and preferably at least 90 volume percent of the clustershaving a mean size that is at least 5 times the mean diameter of theprimary particles. The primary particles may be the nanoparticles havinga mean size as previously described. In some embodiments, thenanoparticles are monodisperse, having a coefficient of variation orrelative standard deviation, expressed as a percentage and defined asthe ratio of the nanoparticle size standard deviation (σ) to thenanoparticle size mean (μ), multiplied by 100%, of less than 25%,preferably less than 10%, preferably less than 8%, preferably less than6%, preferably less than 5%. In a preferred embodiment, thenanoparticles are monodisperse, having a nanoparticle size distributionranging from 80% of the average particle size to 120% of the averagenanoparticle size, preferably 85 to 115%, preferably 90 to 110% of theaverage particle size. In another embodiment, the nanoparticles are notmonodisperse.

In some embodiments, the polyolefin-perovskite nanocomposite issubstantially free of non-perovskite inorganic nanomaterials. Examplesof non-perovskite inorganic nanomaterials include titanium dioxidenanomaterials, zinc oxide nanomaterials, silica nanomaterials,nanoclays, metal nanomaterials such as silver nanoparticles, goldnanoparticles, copper nanoparticles, and platinum nanoparticles, ironoxide nanomaterials, aluminum oxide nanomaterials calcium carbonatenanomaterials, magnesium oxide nanomaterials. In some embodiments, thepolyolefin-perovskite nanocomposite is substantially free of carbonnanomaterials. Examples of carbon nanomaterials include carbonnanotubes, fullerenes, fullerene whiskers, carbon nanobuds, carbonnanoscrolls, activated carbon, carbon black, graphene, and grapheneoxide.

The mixing may be performed using equipment such as a V blender, aribbon blender, a twin-screw continuous blender, a single screw blender,a double cone blender, a planetary mixer, a double planetary mixer, apaddle mixer, a tumbling mixer, a drum blender, a horizontal mixer, orthe like.

The method next involves optionally milling the mixture to form acomposite powder. The mixture may be milled by a technique such asmilling, grinding, ball milling, chopping, pulverizing, crushing,pounding, mincing, shredding, smashing, fragmenting, or anothertechnique that may be used to reduce a material to small particles. Insome embodiments, the milling may take place using a mill, ball mill,rod mill, autogenous mill, semi-autogenous grinding mill, pebble mill,buhrstone mill, burr mill, tower mill, vertical shaft impactor mill, alow energy milling machine, grinder, pulverizer, mortar and pestle,blender, crusher, or other implement used to reduce a material to smallparticles. In some embodiments, the milling is ball milling. In someembodiments, the ball milling takes place in a high-energy ball mill.Non-limiting examples of milling media (i.e. bowl and balls) includezirconium dioxide, tungsten carbide, silicon nitride, and alumina. Inone embodiment, zirconium dioxide milling media is employed to minimizecontamination of the powder mixture. The balls used for milling may havea diameter of 200 to 1,000 preferably 300 to 900 preferably 400 to 800preferably 600 to 650 though balls with diameters smaller than 200 orgreater than 1,000 may be used. In one embodiment, a weight ratio of theballs to the powder mixture ranges from 4:1 to 35:1, preferably from 5:1to 30:1, preferably from 7.5:1 to 25:1, preferably from 9:1 to 15:1. Insome embodiments, the milling is performed in an inert atmosphere,preferably provided by inert gas such as argon gas, though in anotherembodiment, the milling may be performed in air. In some embodiments,the milling is performed at ambient temperature (i.e. 23 to 26° C.). Themixture may be milled for up to 10 hours, or up to 5 hours, or up to 2hours, preferably for 10 to 90 minutes, preferably for 30 to 75 minutes,preferably for 35 to 50 minutes, preferably for 40 minutes. Ahigh-energy ball milling apparatus may use a rotation rate of 500 to10,000 rpm, preferably 750 to 5,000 rpm, preferably 1,000 to 3,250 rpm,preferably 1,025 to 2,500 rpm, preferably 1,050 to 2,000 rpm.Preferably, the ball milling decreases the size of the particles by30-95%, preferably 40-90%, more preferably 60-90% relative to a size ofthe particles before the ball milling.

In some embodiments, the composite powder comprises particles ofpolyolefin and particles of perovskite nanomaterial. In someembodiments, the particles of polyolefin have a particle size of 1 nm to1000 μm, preferably 10 nm to 500 μm, preferably 100 nm to 100 μm,preferably 500 nm to 50 μm. In some embodiments, the particles ofpolyolefin may have a spherical shape, or may be shaped like cylinders,boxes, blocks, spikes, flakes, plates, ellipsoids, toroids, stars,ribbons, discs, rods, granules, prisms, cones, platelets, sheets,angular chunks, cubes, rectangular prisms, or some other shape. In someembodiments, the particles of polyolefin may be substantially spherical,meaning that the distance from the particle centroid (center of mass) toanywhere on the particle outer surface varies by less than 30%,preferably by less than 20%, more preferably by less than 10% of theaverage distance. In some embodiments, the particles of polyolefin arein the form of blocks, granules, rectangular prisms, or angular chunks,having a mean size in a range as previously described and having alargest dimension that is 50 to 500%, preferably 75 to 400, preferably100 to 350%, preferably 150 to 250% of the range previously describedand a smallest dimension that is 5 to 150, preferably 10 to 125,preferably 15 to 100, preferably 25 to 75% of the range previouslydescribed. In some embodiments, the particles of polyolefin aremonodisperse, having a coefficient of variation or relative standarddeviation, expressed as a percentage and defined as the ratio of theparticle size standard deviation (α) to the particle size mean (μ),multiplied by 100%, of less than 25%, preferably less than 10%,preferably less than 8%, preferably less than 6%, preferably less than5%. In a preferred embodiment, the particles of polyolefin aremonodisperse, having a particle size distribution ranging from 80% ofthe average particle size to 120% of the average particle size,preferably 85 to 115%, preferably 90 to 110% of the average particlesize. In another embodiment, the particles of polyolefin are notmonodisperse.

The method next involves molding the composite powder to form acomposite plate. In some embodiments, the molding is performed via blowmolding, compression molding, extrusion molding, injection molding,laminating, matrix molding, rotational molding, spin casting, transfermolding, thermoforming, vacuum forming, or a similar technique known byone of ordinary skill in the art. In some embodiments, the molding iscompression molding. In preferred embodiments, the compression moldingis performed with a hot press mold. In some embodiments, the temperatureof the compression molding is 30 to 177° C., preferably 35 to 172° C.,preferably 40 to 167° C., preferably 50 to 162° C., preferably 80 to160° C., preferably 100 to 155° C., preferably 125 to 152.5° C.,preferably 150° C. In some embodiments, the compression molding isperformed at a pressure of 0.01 bar to 150 bar, preferably 0.1 bar to100 bar, preferably 0.15 bar to 75 bar, preferably 0.25 bar to 50 bar,preferably 0.4 bar to 25 bar, preferably 0.5 bar to 15 bar. In someembodiments, the compression molding involves application of pressurefor 1 to 20 minutes, preferably 2 to 19 minutes, preferably 3 to 18minutes, preferably 4 to 17 minutes, preferably 5 to 15 minutes. In someembodiments, the compression molding comprises two steps performed atdifferent pressures in the range specified above, each step lasting atime in the range specified above. In some embodiments, the first stepis performed at a pressure of 0.1 to 0.9 bar, preferably 0.2 to 0.8 bar,preferably 0.3 to 0.7 bar, preferably 0.4 to 0.6 bar, preferably 0.45 to0.55 bar, preferably 0.5 bar for 1 to 20 minutes, preferably 2.5 to 17.5minutes, preferably 5 to 15 minutes, preferably 7.5 to 12.5 minutes,preferably 10 minutes. In some embodiments, the second step is performedat a pressure of 10 to 150 bar, preferably 11 to 100 bar, preferably 12to 75 bar, preferably 13 to 50 bar, preferably 14 to 25 bar, preferably14.5 to 15.5 bar, preferably 15 bar for 1 to 20 minutes, preferably 2 to15 minutes, preferably 3 to 10 minutes, preferably 4 to 7.5 minutes,preferably 5 minutes. The composite plate comprises a polyolefin matrixand particles of perovskite nanomaterial. In some embodiments, theparticles of perovskite nanomaterial are uniformly distributedthroughout the polyolefin matrix. In some embodiments, the particles ofpolyolefin present in the composite powder are formed into thepolyolefin matrix of the composite plate by sintering of the particlesof polyolefin. In alternative embodiments, the particles of polyolefinpresent in the composite powder are formed into the polyolefin matrix ofthe composite plate by melting of the particles of polyolefin. Inpreferred embodiments, the composite plate has a thickness of 1 μm to100 mm, preferably 10 μm to 50 mm, preferably 100 μm to 25 mm.

In some embodiments, the composite plate has a real dielectricpermittivity of 2.0 to 3.0 at 1 kHz, preferably 2.1 to 2.75, preferably2.2 to 2.5, preferably 2.25 to 2.45, preferably 2.3 to 2.4 at 1 kHz.

The composite plate is then subjected to an AC voltage to form thepolyolefin-perovskite nanomaterial composite. In some embodiments, theAC voltage is 1 to 50 kV, preferably 2.5 to 47.5 kV, preferably 5 to 45kV, preferably 7.5 to 42.5 kV, preferably 10 to 40 kV, preferably 12.5to 35 kV, preferably 15 to 30 kV, preferably 17.5 to 25 kV, preferably20 kV. The AC voltage applied divided by the distance which separatesthe supporting ground electrode and the needle electrode is preferablybelow the breakdown voltage of the polyolefin measured in kV/cm. Inpreferred embodiments, the AC voltage has a frequency of 50 to 70 Hz,preferably 55 to 65 Hz, preferably 60 Hz. In some embodiments, the ACvoltage is applied by placing the composite plate on a supporting groundelectrode and placing a needle electrode into the composite plate suchthat the needle electrode does not contact the supporting groundelectrode (a situation which would result in a short circuit). In someembodiments, the supporting ground electrode and needle electrode areseparated by a distance of at least 30%, preferably at least 40%,preferably at least 50%, preferably at least 55%, preferably at least60%, preferably at least 70%, preferably at least 75%, preferably atleast 80%, preferably at least 85%, preferably at least 90% of athickness of the composite plate. In some embodiments, the supportingground electrode, composite plate, and needle electrode are immersed ina non-conductive liquid medium during the subjecting. Examples ofnon-conductive liquid media for the aforementioned subjecting includesilicon oil, mineral oil, vegetable oil, non-conductive coolant,glycerol, ethylene glycol, propylene glycol, and the like, but excludingdistilled water. In some embodiments, the non-conductive liquid mediumis mineral oil.

The applied AC voltage induces electrical damage or partial dielectricbreakdown in the polyolefin matrix. In some embodiments, the electricaldamage or partial dielectric breakdown is a voltage-induced phenomenon.In some embodiments, current may flow from the needle electrode to thesupporting ground electrode, but such a current is not necessary for theelectrical damage or partial dielectric breakdown of the polyolefin. Insome embodiments, the applied AC voltage induces electrical damage orpartial dielectric breakdown without a flow of current between theelectrodes. This electrical damage causes the formation of electricallyand thermally conductive pathways. Initially, these electrically andthermally conductive pathways form at the needle electrode and propagateoutward from the needle electrode. As these electrically and thermallyconductive pathways propagate, the pathways branch and form a dendriticstructure beginning at the site of the needle electrode and travelingoutward from it in a direction generally toward the supporting groundelectrode. The direction generally toward the supporting groundelectrode may be characterized as a cone the sides of which encompassthe entirety of the electrically and thermally conductive pathways anddescribed by an angle at which the sides meet. In some embodiments, thecone has an angle of less than 180°, preferably less than 150°,preferably less than 120°, preferably less than 90°, preferably lessthan 60°. In some embodiments, the ratio of the maximum horizontaldistance from the needle electrode to an electrically and thermallyconductive pathway to the maximum vertical distance from the needleelectrode to an electrically and thermally conductive pathway is 1:1 to1:100, preferably 1:2 to 1:90, preferably 1:3 to 1:80, preferably 1:4 to1:75, preferably 1:5 to 1:60, preferably 1:6 to 1:50, preferably 1:7 to1:40, preferably 1:8 to 1:35, preferably 1:9 to 1:30, preferably 1:10 to1:25. As used herein, horizontal means in a direction perpendicular tothe direction of the shortest line spanning from the needle electrode tothe supporting ground electrode. As used herein, vertical means in adirection parallel to the direction of the shortest line spanning fromthe needle electrode to the supporting ground electrode. The abovedescription of the direction generally toward the supporting groundelectrode defines the orientation of the electrically and thermallyconductive pathways and the preferential propagation in a directionparallel to the direction of the shortest line spanning from the needleelectrode to the supporting ground electrode compared to the propagationin a direction perpendicular to the direction of the shortest lineimagined spanning from the needle electrode to the supporting groundelectrode makes the electrically and thermally conductive pathwaysoriented electrically and thermally conductive pathways and distinctfrom non-oriented electrically and thermally conductive pathways, whichwould be characterized by isotropic propagation outward from the needleelectrode. The shape of the dendritic structure of the orientedelectrically and thermally conductive pathways is also known as a“lightning tree” or “Lichtenberg figure”.

In some embodiments, the oriented electrically and thermally conductivepathways have a higher dielectric permittivity than portions of thecomposite lacking said pathways. In some embodiments, the presence ofthe oriented electrically and thermally conductive pathways imparts untothe composite a higher dielectric permittivity compared to a compositelacking said pathways.

In some embodiments, the oriented electrically and thermally conductivepathways are comprised of hollow channels in the polyolefin matrix. Insome embodiments, the oriented electrically and thermally conductivepathways are comprised of material formed from electrical damage orpartial dielectric breakdown of the polyolefin matrix that has adistinct composition from the polyolefin matrix. Such distinction maycome in the form of a different crystallinity or percent crystallinity,a different average chain length, a different percent crosslinking, adifferent crosslinking density, oxidation of the polyolefin,carbonization of the polyolefin, charring of the polyolefin, combustionof the polyolefin, or depolymerization of the polyolefin. In someembodiments, the application of the AC voltage results in melting of thepolyolefin matrix localized to the oriented electrically and thermallyconductive pathways. Such melting may change the properties of thepolyolefin such as different crystallinity or percent crystallinity,percent crosslinking, or crosslinking density of the polyolefin. In someembodiments, the application of the AC voltage results in changes to thechemical structure of the polyolefin such as oxidation, carbonization,charring, combustion, or depolymerization of the polyolefin. In someembodiments, the aforementioned changes to the chemical structure of thepolyolefin are the result of thermal processes. In some embodiments, theaforementioned changes to the chemical structure of the polyolefin arethe result of electrochemical processes. In some embodiments, theaforementioned changes to the chemical structure of the polyolefin arethe result of both thermal and electrochemical processes. The orientedelectrically and thermally conductive pathways may originate at eitherthe site of the needle electrode, branch from an existing orientedelectrically and thermally conductive pathway, or from a particle of theperovskite nanomaterial embedded in the polyolefin matrix. The orientedelectrically and thermally conductive pathways may terminate at either aparticle of the perovskite nanomaterial embedded in the polyolefinmatrix or a surface of the nanocomposite. In some embodiments, a singleoriented electrically and thermally conductive pathway, acts as aportion of a path along which electricity may flow, the path comprisingat least one oriented electrically and thermally conductive pathway andoptionally comprising one or more additional oriented electrically andthermally conductive pathways and/or one or more particles of perovskitenanomaterial.

In some embodiments, the aforementioned hollow channels have a meanthickness of 0.01 to 2 μm, preferably 0.05 to 1.75 μm, preferably 0.1 to1.5 μm, preferably 0.15 to 1.25 μm, preferably 0.2 to 1.0 μm, preferably0.25 to 0.9 μm. In some embodiments, the material formed from electricaldamage or partial dielectric breakdown of the polyolefin matrix ispresent as tubes having a mean thickness of 0.01 to 2 μm, preferably0.05 to 1.75 μm, preferably 0.1 to 1.5 μm, preferably 0.15 to 1.25 μm,preferably 0.2 to 1.0 μm, preferably 0.25 to 0.9 μm. In someembodiments, the aforementioned hollow channels or tubes have a taperedshape, meaning the thickness of the hollow channel or tube decreases by10 to 90%, preferably by 15 to 85%, preferably by 20 to 80%, preferablyby 25 to 75% when measured along the hollow channel or tube from a thickend (one having a greater thickness) to a thin end (one have a lesserthickness). In alternative embodiments, the hollow channels or tubes donot have a tapered shape. In some embodiments, a hollow channel or tubehas a maximum thickness that is less than 250%, preferably less than225%, preferably less than 200%, preferably less than 175%, preferablyless than 150% of the mean thickness of that hollow channel or tube. Insome embodiments, a hollow channel or tube has a minimum thickness thatis greater than 10%, preferably greater than 25%, preferably greaterthan 35%, preferably greater than 50% of the mean thickness of thathollow channel or tube. In some embodiments, two or more individualhollow channels or tubes may intersect to form regions in which theoverall size of the region is greater than the thickness of anindividual hollow channel or tube.

In some embodiments, the number and extent of the oriented electricallyand thermally conductive pathways may be changed by the duration of thesubjecting of the composite to the AC voltage. In some embodiments, themaximum distance from the end of the needle electrode to the end of anoriented electrically and thermally conductive pathway is 1 to 5 mm,preferably 1.5 to 4.5 mm, preferably 2 to 4 mm, preferably 2.1 to 3.9mm, preferably 2.2 to 3.8 mm, preferably 2.3 to 3.7 mm, preferably 2.4to 3.6 mm, preferably 2.5 to 3.5 mm, preferably 2.6 to 3.4 mm,preferably 2.7 to 3.3 mm, preferably 2.8 to 3.2 mm, preferably 2.9 to3.1 mm after subjecting the composite to the AC voltage for a durationof 500 to 1500 seconds, preferably 550 to 1450 seconds, preferably 600to 1400 seconds, preferably 650 to 1350 seconds, preferably 700 to 1300seconds, preferably 750 to 1250 seconds, preferably 800 to 1200 seconds,preferably 850 to 1150 seconds, preferably 900 to 1100 seconds,preferably 1000 to 1050 seconds, preferably 1025 seconds. In someembodiments, increasing the number and extent of the orientedelectrically and thermally conductive pathways increases the electricaland/or thermal conductivity of the polyolefin-perovskite nanomaterialcomposite. In some embodiments, increasing the number and extent of theoriented electrically and thermally conductive pathways increases thedielectric permittivity of the polyolefin-perovskite nanomaterialcomposite. In some embodiments, increasing the number and extent of theoriented electrically and thermally conductive pathways hasdisadvantageous effects on other properties of the polyolefin-perovskitenanomaterial composite such as the Young's modulus, toughness,ductility, and % elongation. In some embodiments, the subjecting of theAC voltage is performed for a time to achieve desired electricalconductivity, thermal conductivity, Young's modulus, toughness,ductility, and % elongation of the polyolefin-perovskite nanomaterialcomposite.

This method may be distinguished from method for determining thebreakdown voltage of a polymer or polymer composite using a needleelectrode and a supporting ground electrode in the following ways.First, to determine a voltage at which total electrical breakdownoccurs, a voltage at least equal to the breakdown voltage must beapplied. While lower voltages are necessarily applied before reachingthe breakdown voltage, a method for determining the breakdown voltagecontinues to apply higher voltages until total electrical breakdownoccurs. The method described here, however, relies on voltages below thebreakdown voltage for the polyolefin. The voltage is high enough tocause electrical damage to the polyolefin, but is not high enough tocause total dielectric breakdown. Second, the method described here isreliant on tailoring the number and extent of the electrically andthermally conductive pathways present in the material to achieve adesired value of electrical and/or thermal conductivity and/ordielectric permittivity. Thus, it is advantageous to control the numberand extent of the electrically and thermally conductive pathways presentin the polyolefin-perovskite nanomaterial composite in order to balancethe advantageous effects these pathways have on the electrical andthermal conductivity and/or dielectric permittivity of the compositewith the disadvantageous effects these pathways may have on otherproperties of the composite such as the Young's modulus, toughness,ductility, and % elongation. A method for determining the breakdownvoltage has no need to take these other properties into account andwould be rendered useless if the method was aborted before totaldielectric breakdown occurred because of a change in a property such astoughness.

In some embodiments, the polyolefin-perovskite nanomaterial compositehas a thermal conductivity thermal conductivity of 0.1 Wm⁻¹K⁻¹ to 500Wm⁻¹K⁻¹, preferably 0.2 Wm⁻¹K⁻¹ to 400 Wm⁻¹K⁻¹, preferably 0.3 Wm⁻¹K⁻¹to 300 Wm⁻¹K⁻¹, preferably 0.4 Wm⁻¹K⁻¹ to 200 Wm⁻¹K⁻¹, preferably 0.5Wm⁻¹K⁻¹ to 150 Wm⁻¹K⁻¹, preferably 0.6 Wm⁻¹K⁻¹ to 100 Wm⁻¹K⁻¹. In someembodiments, the polyolefin-perovskite nanomaterial composite has anelectrical conductivity of 10⁻¹² S/m to 10² S/m, preferably 10⁻¹¹ to 10¹S/m, preferably 10⁻¹⁰ S/m to 10° S/m, preferably 10⁻⁹ S/m to 10⁻¹ S/m,preferably 10⁻⁸ S/m to 10⁻² S/m. In some embodiments, thepolyolefin-perovskite nanomaterial composite has a dielectricpermittivity of 3.1 to 50 at 1 kHz, preferably 3.25 to 40, preferably3.5 to 35, preferably 4.0 to 30, preferably 4.5 to 25, preferably 4.75to 22.5, preferably 5.0 to 20 at 1 kHz.

According to a second aspect, the present disclosure relates to apolyolefin-perovskite nanomaterial composite. The composite comprises apolyolefin matrix, perovskite nanomaterial, and oriented electricallyand thermally conductive pathways formed from partial electrical damageof the polyolefin matrix. In some embodiments, the polyolefin matrix ispresent in an amount of 90 to 99 wt %, preferably 95 to 98 wt %,preferably 96 to 97.75 wt %, preferably 96.5 to 97.5 wt %, preferably 97wt % based on a total weight of the composite. In some embodiments, theperovskite nanomaterial is present in an amount of 1 to 10 wt %,preferably 2 to 5 wt %, preferably 2.25 to 4 wt %, preferably 2.5 to 3.5wt %, preferably 3 wt % based on a total weight of the composite.

In some embodiments, the polyolefin is polyethylene as described above.In some embodiments, the polyethylene is low-density polyethylene (LDPE)as described above. In preferred embodiments, the polyolefin is LDPEhaving a density as described above. In preferred embodiments, thepolyolefin is LDPE having a melt flow index as described above.

The perovskite nanomaterial may be a perovskite material as describedabove. In some embodiments, the perovskite nanomaterial is bariumtitanate. In some embodiments, the perovskite nanomaterial is present asnanoparticles as described above.

The electrically and thermally conductive channels take the form of adendritic structure beginning at the site of the needle electrode andtraveling outward from it in a direction generally toward the supportingground electrode as described above.

In some embodiments, the oriented electrically and thermally conductivepathways are comprised of hollow channels in the polyolefin matrix asdescribed above. In some embodiments, the oriented electrically andthermally conductive pathways are comprised of material formed from fullor partial dielectric damage of the polyolefin matrix that has adistinct chemical composition from the polyolefin matrix as describedabove. In some embodiments, a single oriented electrically and thermallyconductive pathway, acts as a portion of a path along which electricitymay flow, the path comprising at least one oriented electrically andthermally conductive pathway and optionally comprising one or moreadditional oriented electrically and thermally conductive pathwaysand/or one or more particles of perovskite nanomaterial as describedabove.

In some embodiments, the polyolefin-perovskite nanomaterial compositehas a thermal conductivity thermal conductivity as described above. Insome embodiments, the polyolefin-perovskite nanomaterial composite hasan electrical conductivity as described above. In some embodiments, thepolyolefin-perovskite nanomaterial composite has a dielectricpermittivity as described above.

The examples below are intended to further illustrate protocols forpreparing, characterizing the polyolefin-perovskite nanomaterialcomposite and uses thereof, and are not intended to limit the scope ofthe claims.

EXAMPLES

Preparation of the Composite Block

A polyethylene/barium titanate nanoparticle composite was prepared by aball milling process. First, barium titanate nanoparticles were manuallypremixed into polyethylene powder. The mixture consisted of 97 wt % ofpolyethylene with 3 wt % of barium titanate nanoparticles. Thepolyethylene was an additive free, low density polyethylene (LDPE)powder having a density of 0.922 g/cm³, melt flow index of 0.4 g/10 minand a typical particle size distribution with 95% of particles less than500 purchased from Marplex Australia. The powder mixture was then ballmilled in a high-energy shaker mill. Milling was performed in azirconium oxide crucible with a weight ratio of balls to powder mixtureof 10:1. Milling was performed in air at ambient temperature (23° C.) ata rotation rate of 1050 to 2000 rpm. Total milling time was 40 minutes.The obtained nanocomposites powder was press-molded to form thin blocksusing a hot press and then, a sharp needle was casted into polyethylenecomposite block to form a needle electrode geometry. The press-moldingwas performed at a temperature of 150° C. The press-molding used atwo-step process, the first step pressing at 0.5 bar for 10 minutes, andthe second step pressing at 15 bar for 5 minutes. The polyethylenecomposite block had a width of 30 mm, a height of 30 mm, and a thicknessof 10 mm. The separation between the electrodes was 3 mm.

Application of the AC Voltage

The complete setup was immersed in mineral oil. Subsequently, a constantAC high voltage of 20 kV and 60 Hz was applied between the sharp needleand the plane (ground) electrode. A depiction of the setup used for theapplication of the AC voltage is shown in FIG. 1, with the needleelectrode (101), composite plate (102), non-conductive liquid medium(103), and supporting ground electrode (104) visible.

FIGS. 2A-2C depict the possible mechanism of tree growth in the polymermatrix filled with barium titanate nanoparticles. The needle electrodeis shown embedded in the polyolefin matrix with barium titanatenanoparticles dispersed in it and supported by the supporting groundelectrode. Over a period of time, high local electric stress leads tothe formation of the conducting channel, which could initiate theelectrical tree from the needle (FIG. 2A). After propagating from theneedle electrode, through the polymer matrix, along the barium titanatenanoparticles interface, but not yet reaching the supporting groundelectrode, the conductive trees propagate to another barium titanatenanoparticle through the polymer matrix (FIG. 2B). After propagatingfrom the needle electrode, through the polymer matrix, along the bariumtitanate nanoparticles interface, and after reaching the supportingground electrode, the conductive trees bridge the gaps between bariumtitanate nanoparticles and form a plurality of oriented electrically andthermally conductive pathways which leads to an improvement in theelectrical and thermal conductivity and dielectric permittivity of thepolymer composite (FIG. 2C).

The final dielectric permittivity and electrical and thermalconductivity of the composite can be tuned by controlling the time (t₁)of the applied high voltage. As t₁ increases the number of propagatedtrees increases leading to an improved electrical conductivity. Thetrees had an average growth rate of 0.0029 mm/sec. Total time of theapplied high voltage was 1025 to 1027 seconds for a sample withelectrode separation of 3 mm.

To reach high dielectric permittivity and electrical and thermalconductivity and protect the nanocomposite material from totaldielectric breakdown, the applied voltage should be stopped a fewseconds before the dielectric breakdown takes place.

The invention claimed is:
 1. A polyolefin-perovskite nanomaterialcomposite, comprising: a polyolefin matrix in an amount of 90 to 99 wt%, based on a total weight of the polyolefin-perovskite nanomaterialcomposite; perovskite nanomaterial present in an amount of 1 to 10 wt %,based on a total weight of the polyolefin-perovskite nanomaterialcomposite; and oriented electrically and thermally conductive pathwaysthat are hollow channels and/or electrically damaged polyolefin matrixhaving a chemical composition different from the polyolefin matrix,wherein the oriented electrically and thermally conductive pathways havea length of from 1 to 5 mm and a tapered shape with mean thickness of0.05 to 2 μm.
 2. The polyolefin-perovskite nanomaterial composite ofclaim 1, wherein the polyolefin matrix comprises polyethylene.
 3. Thepolyolefin-perovskite nanomaterial composite of claim 2, wherein thepolyethylene is low density polyethylene.
 4. The polyolefin-perovskitenanomaterial composite of claim 3, wherein the low density polyethylenehas a density of 0.88 to 0.96 g/cm³ and a melt flow index of 0.2 to 2.5g/10 minutes.
 5. The polyolefin-perovskite nanomaterial composite ofclaim 1, wherein the perovskite nanomaterial is barium titanatenanoparticles.
 6. The polyolefin-perovskite nanomaterial composite ofclaim 1, wherein the oriented electrically and thermally conductivepathways comprise dendritic conductive channels in the polyolefin matrixwhich terminate at and originate from at least one selected from thegroup consisting of an exterior surface of the composite, a channelcreated by the needle electrode, and a particle of the perovskitenanomaterial.
 7. The polyolefin-perovskite nanomaterial composite ofclaim 1, wherein the polyolefin-perovskite nanomaterial composite has athermal conductivity of 0.1 Wm⁻¹K⁻¹ to 500 Wm⁻¹K⁻¹, an electricalconductivity of 10⁻¹² S/m to 10² S/m, and a dielectric permittivity of3.1 to 50 at 1 kHz.
 8. The polyolefin-perovskite nanomaterial compositeof claim 1, wherein the electrically and thermally conductive pathwaysoriginate at a point and propagate outward from the point as acone-shaped dendritic structure.